Plc 5/20

[cjh]

I have a PLC 5/20 that has been sitting on our shelf. I just plugged it up and tried to connect to it with RS Logix. It is asking me for a password. I know for a fact that it has never been given a password. I seem to recall that you could jumper something to get rid of the program in the PLC 5. Does anyone know what effect jumping these jumper pins will have on the CPU? If it only clears the program, this is no problem. I am just concerned that it may also clear the firmware. Please advise if you know the answer.

 

[rogerhollingsworth]

I don't know about jumpers but can't you remove the PLC from its chassis and remove the battery. That should delete the program.

Roger

 

[93lt1]

The foolproof way...

Remove the battery, and wait a while.






Edit:

1 stinking minute....

 

[cjh]

Thanks for the replies. Yea, maybe I was thinking you could jumper something out to expediate the process of draining the cap. You guys have any idea how long it will take for the cap to drain?

 

[93lt1]

The jumper/shorting pins thing sounds familiar to me, but I have never done it, and have no idea which jumper/pins you need to know.

I don't know how long it takes, either. We had a PLC5 wired to switches and lights for training, it had no battery and every time I went to use it, it was back to default, which was OK, because of the application. You usually don't want the last guy's experimental program anyway.

 

[93lt1]

Another idea

If you can see it in RSLinx/RSLogix, try downloading a new program to it.

Not totally sure but, the password thing should be to keep you out of the program, not prevent you from overwriting it.

 

[Ken Roach]

A PLC-5 without a battery and without backplane power will lose it's memory almost instantaneously. You don't have to jumper anything.

SLC-5/0x controllers have a capacitor that will hold memory for days or weeks without a battery. Those are the ones where you have to find two solder pads on the back marked Vdd and GND and jumper those for 60 seconds.